This invention relates generally to a frame for lifting modular building units, shipping containers, or the like. More particularly it relates to a lift frame that may be compactly folded or collapsed to enable it to fit easily into a pickup truck for transportation and which may be adjusted to align the point of lift with the center of gravity of the load being lifted.
In the past, comparatively heavy and bulky loads have been hoisted or lifted by placing them in an embracing sling, cargo net, or chains suspended from the lift ring or hook of a crane or hoist. In some applications the lifting sling has been replaced by a rigid, skeletal lift frame connected between hoisting apparatus and the load to be lifted. A lift frame has the advantage of being more easily attached to a rigid cubical load, and generally simplifies hoisting operations.
However, rigid skeletal lift frames designed to fit large cubical loads are generally quite unwieldy and are extremely difficult to transport and store while fully assembled. Further, since prior lift frames were designed to be suspended from their geometric centers, they were often unsuitable for lifting a load whose center of gravity was located in laterally or radially offset relation to the geometric center of the lift frame. For instance, it has heretofore been impractical to lift a comparatively large, yet fragile, building unit, which has an off-set center of gravity, with any previously known-type of lift frame.